The invention relates to optical railway signals and in particular to those of the type called "searchlight signals" where a disc mask has at the center a circular window from which one or more sources of light, associated to a suitable optical unit, project, selectively on the basis of a control, one of a plurality of coloured lights, usually red, green and yellow.
In the oldest types of railway light signals, of the above specified type, there is provided a single light source or lamp with a respective optical unit which guides and projects a light beam through the window. Suitable chromatic filters are interposed between the lamp and the optical unit and the colors are changed by shifting the filters by mechanical means, electro-magnetically operated.
With the purpose of increasing the intensity of the color light emitted from the disc window, static signals have been introduced having a number of light sources corresponding to that of the signal colors desired. In this case, the device comprises, for each light source, an optical projector, which collects and projects a light beam emitted by the corresponding source, and this beam is taken in a respective light conducting system, or optical guide, which directs it to the signal exit window. The optical unit associated to each light source comprises also the respective chromatic filter, obviously fixed, while the window output unit consists generally of a non-spherical lens, as used, for instance, in the Italian Railways.
The above light conducting system, or optical guide, consists conveniently of bundles of optical fibers, which, starting from each respective light source, are brought to converge into a single beam, whose head is operatively aligned with the signal window.
This invention is aimed at improving the signal, in particular by improving the efficiency of the primary optical unit, or optical unit of collection of each chromatic light beam, and by increasing the brilliancy of the beam emerging from the output head, towards the signal window.
These and other features of the present invention and the resulting advantages, will be understood from the following detailed description of a preferred embodiment of same, given as a non restrictive example, with reference to the attached drawing.